Apparatus for generating positive or negative image output signals from either positive or negative originals

ABSTRACT

An image processing apparatus comprising positive and negative original input signal processing sections respectively converting positive and negative signals obtained by photoelectric scanning of positive and negative originals into positive density signals, and a color processing section for color-processing the positive density signals. The circuits used in the positive original input signal processing section are preferably all included as well in the negative original input signal processing section, so that common circuits may be employed for the two processing sections. This is similarly the case with the positive and negative image output sections. The apparatus also has a positive image output section for converting the output signal of the color processing section into a light amount control signal for a light source for reproducing a positive image, and a negative image output section for converting the output signal of the color processing section into a negative density signal and then into a light amount control signal for forming an intermediate negative so that a desired density is obtained on an ultimate printing photosensitive material when the intermediate negative is printed thereon. During processing in the negative original input signal processing section, a negative original density signal is converted into a density signal representing a corresponding positive image such that the weight of ratio of the Y, M and C color signals is always 1:1:1 for a gray original.

This is a continuation of application Ser. No. 892,454 filed Aug. 4,1986, now U.S. Pat. No. 4,734,763, which is a continuation ofapplication Ser. No. 627,701 filed July 3, 1984, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an image processing apparatus for convertingan image signal detected by photoelectrically scanning an image originalinto a density signal, conducting a color processing of the densitysignal, and then generating a control signal for controlling a lightsource used for forming a reproduced image.

2. Description of the Prior Art

There have heretofore been known image reproducing apparatuses wherein adensity signal obtained by photoelectrically scanning a color imageoriginal is subjected to a color processing such as color correction,sharpness enhancement, or gradation conversion, and the light amountemitted by a reproduction light source is controlled on the basis of thecolor-processed density signal, thereby reproducing an image of adesired quality. In general, in the conventional image reproducingapparatuses, a positive reproduced image is obtained from a positivecolor original. Recently, however, a need has been felt to obtain anintermediate negative from a positive color original, a positive imagefrom a negative original, or an intermediate negative from a negativeoriginal.

However, various problems arise when the signal processing system forobtaining a positive image from a positive original in the conventionalimage reproducing apparatuses is directly used for forming anintermediate negative from a positive original, a positive image from anegative original, or an intermediate negative from a negative original.For example, in the case where an intermediate negative is formed from apositive original or a negative original and an operator controlsvarious parameters in the color processing step in the same manner aswhen a positive image is formed from a positive original, theintermediate negative formed thereby is such that, when the intermediatenegative is ultimately used for printing on a printing photosensitivematerial, an image of a desired density cannot be obtained due to adifference in spectral sensitivity between the photosensitive materialfor the intermediate negative and the ultimate printing photosensitivematerial, or the like. Therefore, when an image is formed on thephotosensitive material for the intermediate negative, the operator musttake into consideration the spectral absorbances of the dyes of thephotosensitive material for the intermediate negative, the spectralsensitivity of the ultimate printing photosensitive material, thespectral intensity of the light source of the printer, and the like.Thus the burden to the operator increases, and he will be unable tocarry out the operation without a certain degree of skill. Further, whenthe original is a negative and a density signal of the negative image issent to the color processing section, it is not always possible for theoperator to accurately control the parameters no matter how skillful hemay be.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide an imageprocessing apparatus which can carry out color processings not only whena positive image is formed from a positive original but also when anintermediate negative is formed from a positive original, a positiveimage from a negative original, and an intermediate negative from anegative original.

Another object of the present invention is to provide an imageprocessing apparatus wherein operations required to be conducted by anoperator at a color processing section for obtaining an intermediatenegative from a positive original, a positive image from a negativeoriginal, and an intermediate negative from a negative original arealmost the same as the operations for obtaining a positive image from apositive original.

The specific object of the present invention is to provide an imageprocessing apparatus which minimizes the size of an image reproducingsystem.

A further object of the present invention is to provide an image inputprocessing apparatus which makes it possible to conduct colorprocessings by the same color processing circuit in both cases where theoriginal is positive and where the original is negative.

A still further object of the present invention is to provide an imageoutput processing apparatus which eliminates the necessity of conductinga density conversion processing for forming a density representing anintermediate negative image in a color processing section even when anegative image is output.

The image processing apparatus adapted to negatives and positives inaccordance with the present invention comprises a positive originalinput signal processing section for receiving an image signal of apositive original and generating therefrom a density signal representinga positive image, and a negative original input signal processingsection for receiving an image signal of a negative original andgenerating therefrom a density signal representing a positive image. Theapparatus is also provided with a color processing section forconducting various color processings of the density signals sent fromthe positive original input signal processing section and the negativeoriginal input signal processing section, and generating color-processeddensity signals as output signals. The apparatus also has a positiveimage output section for receiving the density signal sent from thecolor processing section and generating therefrom a light amount controlsignal for forming a density representing a positive image on an outputphotosensitive material, and a negative image output section forreceiving the density signal sent from the color processing section andgenerating therefrom a light amount control signal for forming a densityrepresenting a negative image on an input photosensitive material.

In the color processing section, when a density representing a positiveimage is formed on an output photosensitive material, a color processingis conducted so as to form the density representing the positive image.When a density representing a negative image is formed on the outputphotosensitive material, a color processing is carried out so that adesired density is obtained on an ultimate printing photosensitivematerial.

In the negative image output section, the color-processed density signalsent from the color processing section, i.e. the density signal forforming a desired density on the ultimate printing photosensitivematerial, is converted into a density signal for forming a densityrepresenting an intermediate negative image for use in printing thedesired density on the ultimate printing photosensitive material. Then,the density signal for forming a density representing an intermediatenegative image is further converted into a light amount control signal.

As the output photosensitive material for forming a density representinga positive image, color paper, a duplicate film, a reversal film, a G(large-size) printing film, or the like is used. As the ultimateprinting photosensitive material, a G printing film, color paper, or thelike is generally used.

As the output photosensitive material for forming a density representinga negative image, a negative film, the aforesaid output photosensitivematerial for forming a density representing a positive image, or thelike is used.

In order to conduct a color processing accurately and simply, it issometimes necessary that the weight ratio among the signals of the threeprimary colors, i.e. yellow (Y), magenta (M) and cyan (C), be alwaysadjusted to 1:1:1 before the color processing is conducted in the colorprocessing section. Therefore, in the negative original input signalprocessing section and the positive original input signal processingsection, image signals should preferably be converted into densitysignals representing a positive image so that the weight ratio among theY, M and C three primary color signals is always 1:1:1.

In the apparatus of the present invention, it is possible to conductcolor processings not only when a positive image is formed from apositive original but also when an intermediate negative is formed froma positive original, a positive image from a negative original, and anintermediate negative from a negative original. Further, the operationsrequired to be conducted by an operator at the color processing sectionfor obtaining an intermediate negative from a positive original, apositive image from a negative original, and an intermediate negativefrom a negative original are almost the same as the operations forobtaining a positive image from a positive original. Accordingly, theapparatus of the present invention is very easy to operate and minimizesthe size of an image reproducing system.

Also, since the density signals supplied to the color processing sectionalways represent a positive image regardless of the type of the original(i.e. positive or negative), it is easy for the operator to controlparameters at the color processing section.

Further, in the negative image output section, the color-processeddensity signal sent from the color processing section for forming adesired density on the ultimate printing photosensitive material isconverted into a density signal for forming a density representing anintermediate negative image for use in printing the desired density onthe ultimate printing photosensitive material. Therefore, in the colorprocessing section, it is not necessary to carry out the densityconversion processing, and it is sufficient to conduct the colorprocessing by considering only the density which should be realized onthe ultimate printing photosensitive material. Accordingly, theoperations of parameters for conducting the color processing, which theoperator must carry out, become simple, and no particular skill isrequired by the operator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an image reproducing system in whichan embodiment of the image processing apparatus in accordance with thepresent invention is employed,

FIG. 2 is a block diagram showing the internal configuration of thepositive original input signal processing section of the apparatus ofFIG. 1,

FIG. 3 is a block diagram showing the internal configuration of thenegative original input signal processing section of the apparatus ofFIG. 1,

FIGS. 4 and 5 are explanatory graphs showing the conversion processingconducted by the negative original input signal processing sectionhaving the internal configuration as shown in FIG. 3,

FIG. 6 is a block diagram showing the internal configuration of thecolor processing section of the apparatus of FIG. 1,

FIG. 7 is a block diagram showing an embodiment of the circuitconfiguration of the color processing section having the internalconfiguration as shown in FIG. 6,

FIG. 8 is a graph showing the hue signals generated by the huediscrimination circuit shown in FIG. 7,

FIG. 9 is a block diagram showing an embodiment of the huediscrimination circuit shown in FIG. 7,

FIG. 10 is a block diagram showing the internal configuration of thepositive image output section of the apparatus of FIG. 1, and

FIG. 11 is a block diagram showing the internal configuration of thenegative image output section of the apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinbelow be described in further detailwith reference to the accompanying drawings.

OVERALL CONFIGURATION OF EMBODIMENT

FIG. 1 is a block diagram showing an image reproducing system in whichan embodiment of the image processing apparatus in accordance with thepresent invention is employed. The image reproducing system comprises aninput drum 1 on which an image original is loaded and photoelectricallyscanned and which outputs an image signal obtained thereby, a positiveoriginal input signal processing section 2 and a negative original inputsignal processing section 3 for converting the image signal into apositive density signal and sending out the positive density signal. Thesystem is also provided with a color processing section 4 for conductinga color processing, such as color correction, of the positive densitysignal and sending out the color-processed positive density signal, apositive image output section 5 and a negative image output section 6for converting the color-processed positive density signal sent from thecolor processing section 4 into a light amount control signal forobtaining a reproduced image and sending out the light amount controlsignal. The system is further provided with a light source 7 and anacousto-optic modulator (AOM) 8 for converting the light amount controlsignals sent from the positive image output section 5 and the negativeimage output section 6 into light amounts, and an output drum 9 on whicha photosensitive material for forming a reproduced image is loaded. Thisembodiment is also provided with a microprocessor 10, so thatcoefficients used for calculation and table data used for conversion inthe positive original input signal processing section 2, the negativeoriginal input signal processing section 3, the color processing section4, the positive image output section 5, and the negative image outputsection 6 can be input from the outside by operating the microprocessor10. Further, coefficients and data handled in the color processingsection 4 can be manually changed by an operator. An image signalobtained by photoelectrically scanning a positive original is input tothe positive original input signal processing section 2, and an imagesignal obtained by photoelectrically scanning a negative original isinput to the negative original input signal processing section 3. When apositive image is formed on the output photosensitive material, theoutput signal of the color processing section 4 is input to the positiveimage output section 5. When a negative image is formed on the outputphotosensitive material, the output signal of the color processingsection 4 is input to the negative image output section 6. Since thisembodiment is constructed as described above, it is possible to conductcolor processings of the density signals by use of the same colorprocessing section 4 for all combinations of the positive and negativeoriginals with the positive and negative reproduced images. Theprocessing sections 2, 3 and 4 and the output sections 5 and 6 shown inFIG. 1 are provided with independent equivalent processing means foreach of the Y, M and C three primary color signals. Therefore, theprocessing sections 2 and 3 and the output sections 5 and 6 shown inFIG. 1 will hereinbelow be described only for one of the Y, M and Cthree primary color signals, whereas the color processing section 4 willbe described for all of the three primary color signals.

CONFIGURATION OF POSITIVE ORIGINAL INPUT SIGNAL PROCESSING SECTION

As shown in FIG. 2, the positive original input signal processingsection 2 comprises a logarithmic conversion circuit 11, an A/Dconverter 12, and a masking processing means 13. The logarithmicconversion circuit 11 receives the image signal obtained byphotoelectric scanning of a positive original and converts the imagesignal into a density signal representing a positive image. The A/Dconverter 12 receives the density signal representing a positive imagesent from the logarithmic conversion circuit 11 and converts the densitysignal into a digital density signal representing a positive image. Themasking processing means 13 converts the density signal sent from theA/D converter 12, i.e. the integral density signal, into an analyticaldensity signal, thereby removing the effect of color impurity of thedyes in the positive original, and sends the digital density signalrepresenting a positive image, which is free from color impurity, to thecolor processing section 4.

CONFIGURATION OF NEGATIVE ORIGINAL INPUT SIGNAL PROCESSING SECTION

As shown in FIG. 3, the negative original input signal processingsection 3 comprises a logarithmic conversion circuit 14, an A/Dconverter 15, a masking processing means 16, an exposure correctiontable generating means 17, an exposure correction means 81, anegative-to-positive conversion means 19, a correction value calculatingmeans 20, and an adder 21. The logarithmic conversion circuit 14receives the image signal obtained by photoelectric scanning of anegative original and converts the image signal into a density signalrepresenting a negative image. The A/D converter 15 receives the densitysignal representing a negative image sent from the logarithmicconversion circuit 14 and converts the density signal into a digitaldensity signal representing a negative image. The masking processingmeans 16 converts the density signal sent from the A/D converter 15,i.e. the integral density signal, into an analytical density signal,thereby removing the effect of color impurity of the dyes in thenegative original, and sends out the digital density signal representinga negative image, which is free from color impurity. The exposurecorrection table generating means 17 generates an exposure correctiontable. On the basis of the exposure correction table sent from theexposure correction table generating means 17, the exposure correctionmeans 18 converts the density signal representing a negative image,which is sent from the masking processing means 16, into a densitysignal representing a negative image when the same object is recordedwith a correct exposure. The negative-to-positive conversion means 19converts the density signal representing a negative image, which is sentfrom the exposure correction means 18, into a density signalrepresenting a positive image. The correction value calculating means 20assists the negative-to-positive conversion means 19 and conducts finedensity correction. The adder 21 adds a correction value supplied by thecorrection value calculating means 20 to the density signal representinga positive image, which is sent from the negative-to-positive conversionmeans 19, and sends the density signal representing a positive imageobtained by the processings in the components of the negative originalinput signal processing section 3 to the color processing section 4.

DIFFERENCE BETWEEN POSITIVE AND NEGATIVE ORIGINAL INPUT SIGNALPROCESSING SECTIONS

As described above, the embodiment of FIG. 1 is provided with two inputsignal processing sections, i.e. the positive original input signalprocessing section 2 and the negative original input signal processingsection 3, to conduct different signal processings of image signals inaccordance with the type of the image original (positive or negative)photoelectrically scanned on the input drum 1. As mentioned above, thesignal processings in the negative original input signal processingsection 3 are more complicated than in the positive original inputsignal processing section 2. This is because the image signal obtainedby photoelectric scanning of a positive original may simply be convertedinto a density signal representing a positive image, whereas the imagesignal obtained by photoelectric scanning of a negative original mustfirst be converted into a density signal representing a negative imageand then be converted into a density signal representing a positiveimage. Further, the signal processings in the negative original inputsignal processing section 3 become complicated because negativeoriginals are recorded under various exposure conditions (e.g. originalsrecorded at different F-numbers within the range of -2 to +4) and adensity signal representing a negative image when the same object isrecorded with a correct exposure cannot be obtained by use of a singlepredetermined exposure correction table. When the image signal obtainedby photoelectric scanning of an original is input to the input signalprocessing section 2 or 3, the operator first judges whether it is anegative or a positive, and then operates a selecting switch toselectively input the image signal to the input signal processingsection 2 or 3.

SIGNAL PROCESSINGS IN NEGATIVE ORIGINAL INPUT SIGNAL PROCESSING SECTION

The signal processings conducted in the negative original input signalprocessing section 3 will hereinbelow be described. As described above,since, unlike positive originals, negative originals are recorded undervarious exposure conditions, a density signal representing a negativeimage when the same object is recorded with a correct exposure cannot beobtained by use of a single predetermined exposure correction table.That is, the exposure correction table used in the exposure correctionmeans 18 must be generated for each original. For this purpose, before anegative original is photoelectrically scanned on the input drum 1, thenegative original is roughly pre-scanned to obtain a density signal, thedensity signal thus obtained is masking-processed and sent to theexposure correction table generating means 17 which detects the exposureconditions under which the negative original was recorded. On the basisof the exposure conditions thus detected, the exposure correction tablegenerating means 17 generates a table for converting the density signalobtained by final scanning into a density signal representing a negativeimage when the same object is recorded with a correct exposure on thenegative photosensitive material. The exposure correction tablegenerated is sent to the exposure correction means 18. Further, in thisembodiment, the microprocessor 10 is used for the exposure correctiontable generating means 17, and the exposure correction table isgenerated by Formula (2) described below. That is, when the shadowdensity of an original as calculated from the density accumulationhistogram of the densities detected by pre-scanning is Ds, the shadowdensity of an original recorded with a correct exposure is Dso, and thecharacteristic curve of the input original photosensitive material asshown in FIG. 4 wherein the abscissa represents the exposure and theordinate represents the density is expressed by

    D=f(x) . . .                                               (1)

where x=log E. Then a table value (D') is obtained by

    D'=f(f.sup.-1 (D)+αx) . . .                          (2)

where Δx=f⁻¹ (Dso)-f⁻¹ (Ds). In the long run, all densities are shiftedin parallel by the exposure Δx corresponding to the density differencebetween Dso and Ds on the characteristic curve of FIG. 4, and it therebybecomes possible to obtain a density signal representing a negativeimage recorded with a correct exposure.

In this embodiment, shadow points of the input original are used forjudging the exposure conditions. However, instead of using the shadowpoint density, it is also possible to use highlight point density orother reference point densities (flesh color, sky color, and the like).

In order to effect the conversion in the negative-to-positive conversionmeans 19, a grey Macbeth chart is first recorded with a correct exposureon a negative photosensitive material and a positive photosensitivematerial and, for example, approximately 90 pairs of data on thedensities on the negative photosensitive material and the densities onthe positive photosensitive material are gathered. Then, these pieces ofdata are interpolation-smoothed, and a conversion curve for converting adensity appearing when a grey object is recorded with a correct exposureon the negative photosensitive material into a density appearing whenthe same object is recorded with a correct exposure on the positivephotosensitive material is generated for each of the three primarycolors (Y, M and C). FIG. 5 is a graph showing the conversion curverepresented by D'i=fi(Di), wherein the abscissa designates the densityon the positive photosensitive material and the ordinate designates thedensity on the negative photosensitive material. The conversion curve isinput to the negative-to-positive conversion means 19. Correction whichcannot be achieved by the negative-to-positive conversion means 19 iscarried out by the correction value calculating means 20. In order toeffect correction value calculation in the correction value calculatingmeans 20, a color Macbeth chart is first recorded with a correctexposure on the negative photosensitive material and the positivephotosensitive material and, for example, approximately 100 pairs ofdata on the densities of each color on the negative photosensitivematerial and the positive photosensitive material are gathered. Sincethese pieces of data are not data on grey, when they are plotted on thegraph of FIG. 5, the results slightly deviate from the conversion curveof FIG. 5. In order to eliminate the deviation, the correction valuecalculating means 20 generates a required correction value ΔDi byFormula (3) using coefficients derived by the method of least squaresfrom approximately 100 pairs of data mentioned above.

    ΔDi≡D'-fi(Di)

    =a.sub.0i +a.sub.1i DY+a.sub.2i DM+a.sub.3i DC

    +a.sub.4i DYDM+a.sub.5i DMDC+a.sub.6i DCDY

    +a.sub.7i DY.sup.2 +a.sub.8i DM.sup.2 +a.sub.9i DC.sup.2   (3)

where i designates Y, M or C, and a0i, a1i, . . . , a9i designate thecoefficients.

When the negative-to-positive conversion means 19 and the correctionvalue calculating means 20 are operated as described above, the densitysignal representing a negative image recorded with a normal exposure,which is output from the exposure correction means 18, is converted tothe density signal representing a positive image recorded with a normalexposure, which is then sent to the color processing section.

As described above, in the negative original input signal processingsection 3, the density signal of an input negative original is convertedinto the density signal representing a negative image recorded with anormal exposure by the former half portion of the processing section 3,and then converted to the density signal representing a positive imagerecorded with a normal exposure by the latter half portion of theprocessing section 3. Accordingly, also for a negative original recordedunder exposure conditions deviating to some extent from the normalconditions, it is possible to obtain a desired density signal at a veryhigh accuracy.

CONFIGURATION OF COLOR PROCESSING SECTION

As shown in FIG. 6, the color processing section 4 comprises a colorcorrection processing means 22, a sharpness enhancement processing means23, and a gradation conversion processing means 24. The color correctionprocessing means 22 receives the density signal representing a positiveimage in which the weight ratio of the Y, M and C three primary colorsignals is 1:1:1 and which is sent from the positive original inputsignal processing section 2 or the negative original input signalprocessing section 3, accurately discriminates the hue on the basis ofthe density signal, and conducts color correction of the density signal.The sharpness enhancement processing means 23 conducts a sharpeningprocessing of the density signal corrected with respect to the color bythe color correction processing means 22. Then, the gradation conversionprocessing means 24 carries out a gradation conversion processing of thedensity signal so that a desired gradation is realized on the targetphotosensitive material (i.e. the output photosensitive material when apositive image is output, or the ultimate printing photosensitivematerial when a negative image is output).

As described above, the color processing section 4 receives the densitysignal representing a positive image in which the weight ratio of the Y,M and C three primary color signals is 1:1:1 and which is sent from theinput signal processing section 2 or 3, and conducts color processingssuch as the color correction, sharpness enhancement, gradationconversion, and the like, of the density signal so that a desireddensity is obtained on the positive output photosensitive material orthe ultimate printing photosensitive material on which an intermediatenegative is printed. Before an original is photoelectrically scanned onthe input drum 1, data on the parameters and tables handled in theprocessing means 22, 23 and 24 is transferred from the microprocessor 10and written into predetermined memories of the processing means 22, 23and 24. The data can be changed by the operator when necessary.

This embodiment has a unique effect with respect to the setting andchange of data in the processing means 22, 23 and 24 of the colorprocessing section 4. That is, the density handled by the operator atthe color processing section is always the density of a positive imagesince only the density signal representing a positive image is generatedby the signal conversion conducted by the input signal processingsections 2 and 3. Also, since signal conversion to a desired type ofimage (positive or negative) reproduced on the output photosensitivematerial is carried out by the image output sections 5 and 6, thedensity output by the color processing section 4 is always of a positiveimage. Thus the color processings are always conducted with respect to apositive-positive system, and the operator can intuitively judge thedensity. Namely, since the color processings are conducted with respectto the positive-positive system, it is sufficient for the operator tochange the data by considering only the color processings (colorcorrection, sharpness enhancement, and gradation conversion) of thedensity formed on the photosensitive material which the operator is mostconcerned about. For example, when an intermediate negative is formed onthe direct output photosensitive material by use of the density signaloutput from the image processing apparatus and then printed on theultimate printing photosensitive material to realize a desired densitythereon, it is possible to eliminate the time and labor the operatorwould have to spend in the case of a conventional apparatus forcalculating a density on the output photosensitive material required forrealizing the desired density on the ultimate printing photosensitivematerial on the basis of the desired density thereon. By "photosensitivematerial which the operator is most concerned about" is meant (1) theultimate printing photosensitive material when a negative image isoutput, or (2) the direct output photosensitive material when a positiveimage is output.

Embodiments of the color correction processing means 22, the sharpnessenhancement processing means 23 and the gradation conversion processingmeans 24 will hereinbelow be described in detail.

OUTLINE OF PROCESSING MEANS OF COLOR PROCESSING SECTION

The color correction processing means 22 generates hue signals of Y(yellow), G (green), C (cyan), B (blue), M (magenta), and R (red) fromthe density signal in which the weight ratio of the Y, M and C threeprimary color signals is always 1:1:1 (hereinafter referred to as theequivalent neutral density signal) and which is input to the colorprocessing section 4. The hue signals are then multiplied by correctioncoefficients and added to each other in the processing means 22, therebyconducting color correction of the Y, M and C three primary colorsignals. The sharpness enhancement processing means 23 generates anunsharp mask signal from an unsharp signal obtained from the imageoriginal and the equivalent neutral density signal. The unsharp masksignal is then multiplied by coefficients and the products are added tothe Y, M and C three primary color signals in the processing means 23,thereby carrying out the sharpness enhancement processing of the Y, Mand C three primary color signals. The gradation conversion processingmeans 24 has data tables for the Y, M and C three primary color signalswherein the input and the output are in one-to-one relation. Arbitrarydata is written in advance as values corresponding to addresses from themicroprocessor 10 into the data tables. On the basis of the data tables,the processing means 24 carries out the gradation conversion processingof the Y, M and C three primary color signals.

CIRCUIT CONFIGURATION OF COLOR PROCESSING SECTION

The circuit configuration of the color processing section willhereinafter be described with reference to FIG. 7. The circuitconfiguration of FIG. 7 includes the circuits for converting the Y, Mand C three primary color signals into the equivalent neutral densitysystem. However, it should be understood that, when the conversion tothe equivalent neutral density system is conducted in the colorprocessing section 4, the conversion need not be carried out in theinput signal processing sections 2 and 3. Digital density signals Y1, M1and C1 sent from the input signal processing sections 2 and 3 are inputto a data selector 115. A digital unsharp signal U1 obtained bydigitally converting an unsharp signal detected from an image originalis input to an unsharp mask signal generating circuit 116 together withthe digital density signal M1. An unsharp mask signal U2 generated bythe circuit 116 is input to the data selector 115. Outputs X11, X21 andX31 of the data selector 115 are respectively input to multiplicationaccumulators 120, 121 and 122. Outputs P1, P2 and P3 of themultiplication accumulators 120, 121 and 122 are respectively input toregisters 126, 127 and 128 via slicing circuits 123, 124 and 125, andalso to data selectors 133, 134 and 135. Outputs YE', ME' and CE' of theregisters 126, 127 and 128 are input to a hue discrimination circuit129. A hue signal CL discriminated by the hue discrimination circuit 129is input to the data selector 115, and a hue address signal CADindicating which hue is output is input to a memory address generatingcircuit 131. A memory address signal MAD generated by the memory addressgenerating circuit 131 is input to memories 117, 118 and 119 via a dataselector 132.

On the other hand, outputs ASY, ASM and ASC of the data selectors 133,134 and 135 are respectively input to table memories 136, 137 and 138used for gradation conversion. Hue signals Y3, M3 and C3 obtained bygradation conversion in the table memories 136, 137 and 138 arerespectively input to D/A converters 145, 146 and 147 via registers 142,143 and 144. Analog hue signals thus obtained from the D/A converters145, 146 and 147 are output as color-corrected hue signals Y4, M4 andC4.

Outputs X12, X22 and X32 of the memories 117, 118 and 119 arerespectively input to the multiplication accumulators 120, 121 and 122.Address signals for the memories 117, 118 and 119 are input thereto viaan address bus AB connected to the microprocessor 10 and via the dataselector 132. Coefficient signals transmitted through a data bus DB areinput into the memories 117, 118 and 119 via input lines DI1, DI2 andDI3 and stored at the address positions specified by the addresssignals. Also, address signals for the table memories 136, 137 and 138are input thereto via the address bus AB via the data selectors 133, 134and 135. Data signals transmitted through the data bus DB are input intothe table memories 136, 137 and 138 via gates 139, 140 and 141 andstored at the address positions specified by the address signals. Thememories 117, 118 and 119 and the table memories 136, 137 and 138 areconstituted by RAM's (random access memories). The memory addressgenerating circuit 131 and the hue discrimination circuit 129 are timedby a timing control circuit 130. Also, timing signals T (t1 to t20)generated by the timing control circuit 130 control the data selector115, the memories 117, 118 and 119, the data selectors 132, 133, 134 and135, the gates 139, 140 and 141, the table memories 136, 137 and 138,and the registers 126, 127, 128, 142, 143 and 144 at the predeterminedtimings.

In the aforesaid configuration, the digital density signals Y1, M1 andC1 of a color original as measured through a three-color separationfilter involve incorrect absorption with respect to the dyesconstituting the color original and the filter, and weights of thedigital density signals Y1, M1 and C1 are not necessarily equal to eachother. However, the incorrectness can be eliminated by conducting theequivalent neutral density conversion by ##EQU1##

The matrix elements bij in Formula (4) are constants determineddepending on the dyes constituting the color original and the colorseparation filter, and are adjusted to such values that, when gray ofthe color original is measured, the levels of YE, ME AND CE are thesame. Formula (4) is constituted by the addition of the products of theconstants bij and the signals Y1, M1, C1 in such manner as, for example,YE=b11.Y1+b12.M1+b13.C1. Therefore, the calculation of Formula (4) canbe achieved by sequentially carrying out the multiplications and theadditions for YE, ME and CE. In the memories 117, 118 and 119,coefficients DI1 (b11 to b14 and k11 to k16), DI2 (b21 to b24 and k21 tok26) and DI3 (b31 to b34 and k31 to k36) transmitted from themicroprocessor 10 via the data bus DB are written in advance at theaddress positions specified by the address signals transmitted from themicroprocessor 10 via the address bus AB. The coefficients b14, b24,b34, k11 to k16, k21 to k26, and k31 to k36 will be described later. Themultiplication accumulators 120, 121 and 122 multiply the digitaldensity signals Y1, M1 and C1 transmitted via the data selector 115 bythe coefficients stored in the memories 117, 118 and 119, and accumulatethe calculation results.

At this time, the timing control circuit 130 first controls to selectthe digital density signal Y1 from the input signals by the timingsignal t1 for the data selector 115, and input the signal Y1 to themultiplication accumulators 120, 121 and 122. The memory address signalMAD of the memory address generating circuit 131 is sent to the addresslines of the memories 117, 118 and 119 via the data selector 132 by thetiming signal t5. As a result, the coefficients b11, b21 and b31 arerespectively output from the memories 117, 118 and 119 and sent to themultiplication accumulators 120, 121 and 122. Thus the multiplicationaccumulators 120, 121 and 122 respectively generate the products b11.Y1,b21.Y1 and b31.Y1 as the outputs P1, P2 and P3. (This timing is referredto as timing I.)

At the next timing II, the digital density signal M1 is selected fromthe data selector 115 and input to the multiplication accumulators 120,121 and 122. The memory address signal MAD of the memory addressgenerating circuit 131 is sent to the memories 117, 118 and 119 via thedata selector 132 to select the coefficients b12, b22 and b32respectively stored therein and input them into the multiplicationaccumulators 120, 121 and 122. In the multiplication accumulators 120,121 and 122, the digital density signal M1 is multiplied by thecoefficients b12, b22 and b32 respectively, and the multiplicationresults are added to the products obtained at the timing I. As a result,b11.Y1+b12.M1, b21.Y1+b22.M1, and b31.Y1+b32.M1 are generated as theoutputs P1, P2 and P3 of the multiplication accumulators 120, 121 and122.

Then, at the next timing III, the digital density signal C1 is selectedfrom the data selector 115 and input to the multiplication accumulators120, 121 and 122. The coefficients b13, b23 and b33 are output from thememories 117, 118 and 119 and input to the multiplication accumulators120, 121 and 122. Therefore, the results of the multiplications and theaccumulation generated as the outputs P1, P2 and P3 of themultiplication accumulators 120, 121 and 122 becomesb11.Y1+b12.M1+b13.C1, b21.Y1+b22.M1+b23.C1, and b31.Y1+b32.M1+b33.C1.

Accordingly, at the timings I, II and III, as the outputs P1, P2 and P3of the multiplication accumulators 120, 121 and 122, the equivalentneutral density signals YE, ME and CE are obtained as expressed byFormulae (5) which are transformed from Formula (4). ##EQU2## Theequivalent neutral density signals YE, ME and CE are respectively storedas YE', ME' and CE' in the registers 126, 127 and 128 via the slicingcircuits 123, 124 and 125. The slicing circuits 123, 124 and 125 operateso that, when the inputs YE, ME and CE are larger than predeterminedmaximums or smaller than predetermined minimums, the predeterminedmaximums or minimums are output. Further, during the timings I, II andIII, the unsharp mask signal U2 is generated by the unsharp mask signalgenerating circuit 116. In this example, the unsharp mask signal U2 iscalculated by U2=M1-U1.

At the next timing IV, the unsharp mask signal U2 is output from thedata selector 115 and input to the multiplication accumulators 120, 121and 122 together with the coefficients b14, b24 and b34 selected andoutput from the memories 117, 118 and 119. The multiplicationaccumulators 120, 121 and 122 multiply the unsharp mask signal U2 by thecoefficients b14, b24 and b34 respectively and add the products to theaccumulated values YE, ME and CE. As a result, YS, MS and CS representedby Formulae (6) are generated as the outputs P1, P2 and P3. ##EQU3##

Further, at the timing V, calculations of selective color correction areconducted. The selective color correction is conducted by YC=YS+YCC,MC=MS+MCC, and CC=CS+CCC by using correction signal YCC, MCC and CCCwhich are represented by ##EQU4##

(Y), (G), (C), (B), (M), and (R) in Formulae (7) are hue signalsobtained by equally dividing all hues as shown in FIG. 8. The huesignals (Y) to (R) are generated by the hue discrimination circuit 129during the timing IV. As is clear from FIG. 8, at most two of the sixhue signals are output for each hue. Therefore, in the multiplicationaccumulators 120, 121 and 122, multiplications by the coefficients kijand additions of the products are conducted for the two hue signals.Namely, at the timing V, the timing control circuit 130 controls tofirst output one of the hue signals (Y) to (R) as the output CL from thehue discrimination circuit 129 and to send it to the multiplicationaccumulators 120, 121 and 122 via the data selector 115. Thecoefficients kij are adjusted by the operator to values suitable forforming desired densities representing a positive image which should berealized on the output photosensitive material or the ultimate printingphotosensitive material. The hue address signal CAD indicating which huesignal is output is transmitted from the hue discrimination circuit 129to the memory address generating circuit 131, and the memory addressgenerating circuit 131 outputs the memory address signal MAD for readingout the coefficients kij corresponding to the hue signal. When thememory address signal MAD is sent to the memories 117, 118 and 119 viathe data selector 132, the coefficients kij stored in advance in thememories, 117, 118 and 119 are selected and output to the multiplicationaccumulators 120, 121 and 122. In the multiplication accumulators 120,121 and 122, the products of the hue signal and the coefficients kij areadded to the previously accumulated values YS, MS and CS. Further, atthe next timing VI, calculations are carried out in the same manner forthe remaining one of the two hue signals, and YC, MC and CC aregenerated as the outputs P1, P2 and P3 of the multiplicationaccumulators 120, 121 and 122.

The hue discrimination circuit 129 may be realized, for example, by acircuit configuration as shown in FIG. 9. Operations of the circuitconfiguration will hereinbelow be described.

Signals YE', ME' and CE' are input to a comparator 148 and a dataselector 150. The comparator 148 compares the levels of YE', ME' and CE'and sends the comparison output signals to a control circuit 149. Forexample, when YE'>ME'>CE', the comparator 148 generates output signalsD1 (YE'>ME'), D2 (ME'>CE'), and D3 (CE'>YE') which are respectively atlogic "1", "1" and "0" levels. On the basis of the output signals D1, D2and D3, the control circuit 149 sends a control signal CT to the dataselector 150 so that the data selector 150 selects and outputs YE' andME' as outputs X1 and X2 at a firt timing, and selects and outputs ME'and CE' at a second timing. Signals YE' and ME' selected as the outputsX1 and X2 of the data selector 150 at the first timing are sent to anaddition input terminal and a subtraction input terminal of asubstracter 151, and the subtraction result of CL=YE'-ME' is obtained asthe output of the subtracter 151. At the second timing, ME' and CE' areselected as the outputs X1 and X2 of the data selector 150, and thesubtraction result of CL=ME'-CE' is obtained as the output of thesubtracter 151. The signals CL generated at the first and second timingscorrespond to the hue signals (Y) and (R).

Multiplications and additions are completed as described above, and thecorrected color signals YC, MC and CC obtained thereby are sent throughthe slicing circuits 123, 124 and 125, and the data selectors 133, 134and 135 into the gradation conversion table memories 136, 137 and 138 asthe address signals ASY, ASM and ASC. The table memories 136, 137 and138 store the data tables in which the inputs and the outputs are inone-to-one relation, and conduct gradation conversion in a desiredmanner on the basis of the data written in advance in conformity withthe addresses. The corrected color signals Y3, M3 and C3gradation-converted by the table memories 136, 137 and 138 are outputfrom the color processing section 4 via the latching registers 142, 143and 144.

When the coefficient signals are written into the memories 117, 118 and119, address signals are output from a computer or the like to theaddress bus AB and input to the address lines of the memories 117, 118and 119 via the data selector 132. At the same time, the coefficientsignals are output to the data bus DB and input to the data input linesDI1, DI2 and DI3 of the memories 117, 118 and 119. Further, the timingsignals t2, t3 and t4 are input to the memories 117, 118 and 119, andthe coefficient signals are thereby sequentially written into thecorresponding address positions as specified. At this time, the dataselector 132 operates to select the address signals sent from theoutside. Also when data signals are written into the table memories 136,137 and 138, address signals sent through the address bus AB are inputto the address lines ASY, ASM and ASC of the table memories 136, 137 and138 via the data selectors 133, 134 and 135. The data signals sentthrough the data bus DB are input to the data input/output lines of thetable memories 136, 137 and 138 via the gates 139, 140 and 141. Further,the timing signals t12, t13 and t14 are input to the table memories 136,137 and 138 and the gradation conversion data signals are sequentiallywritten into the corresponding address positions as specified.

As the coefficients stored in the memories 117, 118 and 119 and the datastored in the table memories 136, 137 and 138, coefficients and datacorresponding to various combinations of image originals with reproducedimages are stored in advance in the microprocessor 10. The coefficientsand data are selected or generated by use of a selecting and generatingmeans (manual or automatic) on the basis of various pieces ofinformation on the image originals and reproduced images, and stored inthe memories 117, 118 and 119 and the table memories 136, 137 and 138.On a front panel of the image processing apparatus are installed digitalswitches (not shown) for facilitating the operations by the operator sothat the operator can change the coefficients and the data.

In the color processing section 4 as described above, since theequivalent neutral density signals representing a positive image areinput to the hue discrimination circuit 129, hue discrimination isconducted accurately and, consequently, color correction processings areachieved accurately.

IMAGE OUTPUT SECTIONS

The positive image output section 5 and the negative image outputsection 6 for converting the density signals representing a positiveimage, which are color-processed and output by the color processingsection 4, into signals for controlling the light amount emitted fromthe exposure light source 7 to the output photosensitive material willhereinafter be described with reference to FIGS. 10 and 11.

CONFIGURATION OF POSITIVE IMAGE OUTPUT SECTION

As shown in FIG. 10, the positive image output section 5 comprises alight amount control signal conversion means 25, and a D/A conversionmeans 26. The light amount control signal conversion means 25 has alight amount control signal conversion table for converting the densitysignal representing a positive image on the output photosensitivematerial, which is output from the color processing section 4, into thelight amount control signal for controlling the light amount necessaryfor forming the density corresponding to the density signal representinga positive image and emitted from the exposure light source 7. The D/Aconversion means 26 subsequently converts the light amount controlsignal to an analog signal.

CONFIGURATION OF NEGATIVE IMAGE OUTPUT SECTION

As shown in FIG. 11, the negative image output section 6 comprises aprinting density conversion means 27, a positive-negative calculationmeans 28, a light amount control signal conversion means 29, and a D/Aconversion means 30. The printing density conversion means 27 and thepositive-negative calculation means 28 convert the density signalrepresenting a positive image on the ultimate printing photosensitivematerial, which is output from the color processing section 4, into adensity signal representing a negative (intermediate negative) image onthe direct output photosensitive material, which is necessary forrealizing the density corresponding to the density signal representing apositive image. The light amount control signal conversion means 29 hasa light amount control signal conversion table for converting thedensity signal representing a negative image on the direct outputphotosensitive material into a light amount control signal forcontrolling the light amount which is necessary for forming the densitycorresponding to the density signal representing a negative image andwhich is emitted from the exposure light source 7. The D/A conversionmeans 30 subsequently converts the light amount control signal to ananalog signal.

DIFFERENCE BETWEEN POSITIVE AND NEGATIVE IMAGE OUTPUT SECTIONS

As described above, this embodiment is provided with the positive imageoutput section 5 and the negative image output section 6, and thedensity signal output from the color processing section 4 is processedin one of the image output sections 5 and 6 according to the type of theimage (positive or negative) which should be formed on the direct outputphotosensitive material, and then be output to the outside of theapparatus. The signal processings in the negative image output section 6is more complicated than those in the positive image output section 5.This is because the signal output from the color processing section isthe density signal representing a positive image, and it is sufficientto simply convert the density signal into the light amount controlsignal for forming a positive density on the direct outputphotosensitive material in the positive image output section 5 whereas,in the negative image output section 6, the density signal must first beconverted into a density signal representing a negative image and theninto the light amount control signal for forming a negative density onthe direct output photosensitive material. Further, the density signalrepresenting a negative image in the negative image output section 6 isthe one which forms a negative (intermediate negative) image realizing adesired positive image on the ultimate printing photosensitive materialwhen printed thereon. In order to convert the density signal output fromthe color processing section 4 into the density signal representing anegative image as mentioned above, complicated signal processings arenecessary. When the output signal of the color processing section 4 isinput to one of the image output sections 5 and 6, the operator operatesa selecting switch to selectively input the output signal to the imageoutput section 5 or 6 according to the type of density (densityrepresenting a positive image or density representing a negative image)on the output photosensitive material which the operator desires.

SIGNAL PROCESSINGS IN NEGATIVE IMAGE OUTPUT SECTION

Signal processings conducted in the negative image output section 6 willhereinbelow be described. The density signal representing a positiveimage to be realized on the printing photosensitive material, which isoutput from the color processing section 4 is input to the printingdensity conversion means 27 in which the density signal is convertedinto a printing density for the printing photosensitive material on thebasis of the printing density conversion table. The printing densitysignal is input to the positive-negative calculation means 28 andconverted by a positive-negative calculation circuit (multiplicationaccumulator) thereof into a density signal representing a negative imageon the output photosensitive material. The density signal representing anegative image is the one which can form an intermediate negativerealizing a desired density on the printing photosensitive material whenprinted thereon. The positive-negative calculation circuit calculates

    Di=C.sub.0i +C.sub.1i Yc+C.sub.2i Mc+C.sub.3i Cc

    +C.sub.4i YcMc+C.sub.5i McCc+C.sub.6i CcYc

    +C.sub.7i Yc.sup.2 +C.sub.8i Mc.sup.2 +C.sub.9i Cc.sup.2   (8)

where Di designates the density representing a negative image on theoutput photosensitive material, and C0i, C1i, . . . , C9i are thecoefficients.

Thereafter, the density signal generated by the calculation means 28 isinput to the light amount control signal conversion means 29 andconverted therein into a light amount control signal for controlling thelight amount of the exposure light source 7 by use of the light amountcontrol signal conversion table.

Setting of the printing density conversion table in the printing densityconversion means 27 and setting of the coefficients C0i, C1i, . . . ,C9i of Formula (8) used for calculation in the positive-negativecalculation means 28 will hereinbelow be described in detail.

As for the setting of the printing density conversion table, it issufficient to store the inverse function of the characteristic curve inthe printing density conversion means 27 in the form of a digitalmemory. The characteristic curve is the curve indicating thecharacteristics of the photosensitive material on a graph wherein theabscissa represents the common logarithm of the exposure E and theordinate represents the photographic density D.

As for the setting of the coefficients C0i, C1i, . . . , C9i of Formula(8), when the printing conditions for the printing photosensitivematerial are known, integration for calculating the printing density onthe printing photosensitive material from the density on the outputphotosensitive material under the same conditions is conducted inadvance for several hundreds of sets of densities (DY, DM, DC) on theoutput photosensitive material by use of a microprocessor or the like.From several hundreds of pieces of data obtained thereby, it is possibleto determine the coefficients C0i, C1i, . . . , C9i satisfying Formula(8) by the method of least squares.

The aforesaid integration is conducted by

    P=-log (∫S.sub.80 J.sub.λ T.sub.λ d.sub.λ /∫S.sub.λ J.sub.λ T.sub.Bλ d.sub.λ) (9)

where λ denotes the wavelength, S.sub.λ denotes the spectral sensitivityof the printing photosensitive material, J.sub.λ designates the spectralintensity of the printer light source, T.sub.λ denotes the spectraltransmittance of the output photosensitive material (T.sub.λ =10^(-D)λwhere D.sub.λ designates the spectral density of the outputphotosensitive material), and T_(B)λ denotes the base spectraltransmittance of the output photosensitive material.

In Formula (9), when the output photosensitive material is for forming anegative image, T_(B)λ is the orange mask spectral transmittance of thephotosensitive material. When the output photosensitive material is nota negative photosensitive material, for example, when it is a duplicatefilm or the like, it is sometimes desired to form a color of a densitycorresponding to the orange mask by use of the Y, M and C three primarycolor signals. In this case, the spectral transmittance obtained byrepresenting the orange mask by the Y, M and C three primary colorsignals (the spectral transmittance is approximately equal to that ofthe aforesaid negative photosensitive material) is substituted forT_(B)λ. As a result, the density Di on the output photosensitivematerial calculated by Formula (8) by use of the coefficients Cijobtained from the sample data is output as the density accommodating thedensity of the orange mask correcting the incorrect absorption on theoutput photosensitive material. That is, it is possible to obtain animage to which the orange mask is applied as in the case of an imageformed on the negative photosensitive material.

Printing density is described in detail in James, The Theory of thePhotographic Process (Macmillan, 1977), pp. 519-523.

After the signal processings are conducted as described above, the lightamount control signal generated by the negative image output section 6is input to the acousto-optic modulator (AOM) 8 and used therein tocontrol the light amount of the exposure light source 7, thereby forminga desired negative image on the output photosensitive material loaded onthe output drum 9.

Also, the light amount control signal generated by the positive imageoutput section 5 is input to the acousto-optic modulator (AOM) 8 andused therein to control the light amount of the exposure light source 7,thereby forming a desired positive image on the output photosensitivematerial loaded on the output drum 9.

In the aforesaid embodiment, the image output sections 5 and 6 areprovided as described above. When the density representing a positiveimage is formed on the output photosensitive material, the light amountcontrol signal for forming the density is output by the positive imageoutput section 5. When the density representing a negative image isformed on the output photosensitive material, the negative image outputsection 6 converts the density which should be realized on the ultimateprinting photosensitive material into the density representing thenegative image on the output photosensitive material and then generatesthe light amount control signal for forming the density. Accordingly,when the color processings are conducted in the color processing section4, it is possible to determine the conversion coefficients and theconversion data by considering only the density representing a positiveimage which should be formed on the output photosensitive material orthe density (representing a positive image) which should be realized onthe ultimate printing photosensitive material. Particularly, when thedensity representing a negative image is formed on the outputphotosensitive material and the conversion coefficients and theconversion data are determined or changed by the operator, it is notnecessary for the operator to calculate the density which should beformed on the output photosensitive material from the density whichshould be realized on the ultimate printing photosensitive material.Thus the burden on the operator is decreased, and the desired densityrepresenting a negative image can readily be formed on the outputphotosensitive material regardless of the skill of the operator.Further, it is possible to always realize the desired density on theultimate printing photosensitive material.

Further, since the positive image output section 5 and the negativeimage output section 6 output the light amount control signals suitablefor the type of the output photosensitive material, it is also possibleto use a photosensitive material which is generally used as a positivephotosensitive material, or the like, as the output photosensitivematerial for forming the density representing a negative image, forexample.

EFFECTS OF EMBODIMENT

The configurations of the components, the signal processings and theeffects of the embodiment of the image processing apparatus inaccordance with the present invention are described above. In theaforesaid embodiment, the signal processings are conducted quickly on areal time basis by use of the digital circuits employing the tablememories and multiplication accumulators, and it is not necessary to uselarge-capacity image memories and circuits for conducting integration.Therefore, it is possible to constitute a small, cheap system.

MODIFICATION OF EMBODIMENT

In the above-described embodiment, the positive original input signalprocessing section 2 and the negative original input signal processingsection 3 are independently provided as the input signal processingsections, and the positive image output section 5 and the negative imageoutput section 6 are independently provided as the image outputsections. In another preferred embodiment of the image processingapparatus in accordance with the present invention, the positiveoriginal input signal processing section 2 and the negative originalinput signal processing section 3 are constituted by common circuits, sothat the circuits of FIG. 3 would be used for both the positive andnegative original input signal processing sections, and the positiveimage output section 5 and the negative image output section 6 areconstituted by common circuits so that the circuits of FIG. 11 would beused for both the positive and negative image output sections. Asdescribed above, the circuit configurations of the positive originalinput signal processing section 2 and the positive image output section5 may be simpler than those of the negative original input signalporcessing section 2 and the negative image output section 6. Therefore,when positive original signals are input and when positive images areoutput, a part of the table memories and a part of the calculationcircuits become unnecessary. In such cases, identity processings areconducted to achieve the common use of the circuits. By "identityprocessings" are meant such processings as make the input signals andthe output signals identical with each other. Table 1 shows the jobswhich the means of the input signal processing section and the imageoutput section conducts in accordance with the type (positive ornegative) of the input original and the type (positive or negative) ofthe output image.

                                      TABLE 1                                     __________________________________________________________________________    Input signal Negative original input                                                                   Positive original input                              processing section                                                            Masking processing means                                                                   Masking processing                                                                        Masking processing                                   Exposure correction means                                                                  Exposure correction                                                                       Identity processing                                               table                                                            Negative-to-positive                                                                       Negative-to-positive                                                                      Identity processing                                  conversion means                                                                           conversion table                                                 Correction value                                                                           Correction calculation                                                                    All coefficients                                     calculating means                                                                          processing  aij = 0                                              Color processing section                                                                    ##STR1##                                                        Image output section                                                          Printing density                                                                           Printing density                                                                          Identity processing                                  conversion means                                                                           conversion table                                                 Positive-negative                                                                          Positive-to-negative                                                                      Identity processing                                  calculation means                                                                          conversion calculation                                           Light amount control                                                                       Light amount control                                                                      Light amount control                                 signal conversion means                                                                    signal conversion table                                                                   signal conversion table                                           Negative image output                                                                     Positive image output                                __________________________________________________________________________

Further, in the above-described embodiment, density correction isconducted in the negative original input signal processing section byuse of the correction value calculating means 20 for carrying out finedensity correction. However, when it is not necessary to conduct strictdensity correction or when the negative original is monochromatic, it ispossible to cascade the exposure correction table of the exposurecorrection means 18 and the negative-to positive conversion table of thenegative-to-positive conversion means 19 and unify them into one table.

Also, it is possible to change the calculation by Formula (3) conductedin the correction value calculating means 20, for example, as shownbelow in accordance with the level of accuracy required.

That is, when a high accuracy is not required, Formula (3) may bechanged to

    Di'-a.sub.0i +a.sub.1i D.sub.Y +a.sub.2i D.sub.M +a.sub.3i Dc

    (=Y, M, C)

When a high accuracy is required, Formula (3) may be changed to

    Di'=a.sub.0i +a.sub.1i D.sub.Y +a.sub.2i D.sub.M +a.sub.3i D.sub.C

    +a.sub.4i D.sub.Y D.sub.M +a.sub.5i D.sub.M D.sub.C +a6.sub.i D.sub.C D.sub.Y

    +a.sub.7i D.sub.Y.sup.2 +a.sub.8i D.sub.M.sup.2 +a.sub.9i D.sub.C.sup.2

    +a.sub.10i D.sub.Y D.sub.M D.sub.C +a.sub.11i D.sub.Y D.sub.M.sup.2

    +a.sub.12i D.sub.Y.sup.2 D.sub.M +

Also, when it is necessary to generate a black separation signal in thecolor processing section 4, it is possible to conduct generation of theblack separation signal simultaneously with the selective colorcorrection by detecting YS, MS and CS from the outputs P1, P2 and P3when calculations up to the timing IV are completed, sending them to ablack separation signal generating circuit, and conducting a calculationfor generating the black separation signal at the timings V and VI.

Further, in the aforesaid embodiment, the coefficients stored in thememories 17, 18 and 19 are stored in advance in the microprocessor 10.However, the coefficients may also be stored in a RAM, a ROM, or thelike.

Furthermore, when a monochromatic negative is formed by three-colorseparation on a monochromatic photosensitive material by use of theoutput signal of the negative image output section 6, it is notnecessary to generate an orange mask as in the case where a colornegative image is formed. That is, the spectral transmittance of themonochromatic photosensitive material (in a non-exposed condition) maybe used as T_(B)λ in Formula (9).

Also, instead of using the digital circuits for carrying out the signalprocessings, it is also possible to conduct the signal processings byuse of analog circuits.

We claim:
 1. An apparatus for processing an image signal forpositive-to-negative conversion in an image output system, whichcomprises means for converting a positive density signal representing apositive image to be printed with a desired density on an ultimatephotosensitive printing material into a positive density printing signalfor producing said positive image with said desired density, and meansfor converting said positive density printing signal into a negativedensity signal representing an intermediate negative image to be printedon an intermediate photosensitive printing material with a density suchthat when said negative image is used to print an image on said ultimatephotosensitive printing material, said positive image with said desireddensity is obtained.
 2. An apparatus as defined in claim 1 wherein saidpositive density signal is converted into said positive density printingsignal via a table memory, and then matrix calculations are conducted onsaid positive density printing signal to convert it into said negativedensity signal.
 3. An apparatus for processing a negative originaldensity signal, obtained by photoelectrically scanning a negativeoriginal and including three primary color signal componentscorresponding to respective primary color contents of said negativeoriginal, which apparatus comprises:first converting means forconverting said negative original density signal into a correctednegative density signal representing a negative image recorded with anormal exposure (neither underexposed nor overexposed), and secondconverting means for converting said corrected negative density signalthus obtained into a positive density signal having three primary colorsignal components and representing a positive image recorded with anormal exposure, a weight ratio of said three primary color signalcomponents of said positive density signal always being equal to apredetermined ratio when said negative original is a gray original. 4.An apparatus for processing a negative original density signal, obtainedby photoelectrically scanning a negative original and including threeprimary color signal components corresponding to respective primarycolor contents of said negative original, which apparatuscomprises:first converting means for converting said negative originaldensity signal into a corrected negative density signal representing anegative image recorded with a normal exposure (neither underexposed noroverexposed), and second converting means for converting said correctednegative density signal thus obtained into a positive density signalhaving three primary color signal components and representing a positiveimage recorded with a normal exposure, a weight ratio of said threeprimary color signal components of said positive density signal alwaysbeing equal to 1:1:1 when said negative original is a gray original.